T1 is a high-speed North-American digital phone line standard created by AT&T. This standard was originally designed to transfer voice digitally, as it has 24 64-Kbps channels. A pair of copper wires makes the transmission and the maximum transfer rate of T1 lines is of 1.544 Mbps.

Several countries use the European telephony standard, which uses 2 Mbps E1 lines.